Pediatric X-ray Imaging

Description

Medical imaging has led to improvements in the diagnosis and treatment of numerous medical conditions in children and adults.

There are many types - or modalities - of medical imaging procedures that are used on children, each of which uses different technologies and techniques. Computed tomography (CT), fluoroscopy, and radiography (conventional X-ray) all use ionizing radiation to generate images of the body. Ionizing radiation is a form of radiation that has enough energy to potentially cause damage to DNA and may elevate a person’s lifetime risk of developing cancer.

CT, radiography, and fluoroscopy all work on the same basic principle: an X-ray beam is passed through the body where a portion of the X-rays are either absorbed or scattered by the internal structures, and the remaining X-ray pattern is transmitted to a detector for recording or further processing by a computer. These exams differ in their purpose:

Radiography - a single image is recorded for later evaluation.

Fluoroscopy - a continuous X-ray image is displayed on a monitor, allowing for real-time monitoring of a procedure or passage of a contrast agent, or “dye” through the body. Fluoroscopy can result in relatively high radiation doses, especially for interventional procedures (such as placing catheters, or other devices inside the body) which require fluoroscopy be administered for a long period of time.

CT - many X-ray images are recorded as the detector moves around the patient's body. A computer reconstructs all the individual images into cross-sectional images or “slices” of internal organs and tissues. A CT exam involves a higher radiation dose than conventional radiography because the CT image is reconstructed from many individual X-ray projections.

Benefits/Risks

X-ray imaging exams are recognized as a valuable medical tool for a wide variety of examinations and procedures including:

noninvasive and painless diagnosis of disease and monitoring of therapy;

support of medical and surgical treatment planning; and

interventional procedures such as placing catheters, stents, or other devices inside the body, or removing blood clots or other blockages.

The individual risk from a necessary imaging exam is generally quite small when compared to the benefit of helping with accurate diagnosis or intervention. Risks from X-ray imaging include risks from exposure to ionizing radiation and possible reactions to the intravenous contrast agent, or “dye” that is sometimes used to improve visualization.

Types of radiation risks include:

tissue effects such as cataracts, skin reddening, and hair loss, which occur at relatively high levels of radiation exposure and are very rare in children; and

a small increase in the possibility that a person exposed to X-rays will develop cancer later in life. Radiation-induced cancer risks depend on the radiation dose, the patient's age at exposure, the sex of the patient (women are more radiosensitive than men), and the organ irradiated.

While the benefit of a clinically appropriate X-ray imaging exam generally far outweighs the risk, efforts should be made to minimize this risk by reducing unnecessary exposure to ionizing radiation. Ionizing radiation exposure to pediatric patients from medical imaging procedures is of particular concern because pediatric patients:

are more radiosensitive than adults (i.e., the cancer risk per unit dose of ionizing radiation is higher);

have a longer expected lifetime for any effects of radiation exposure to manifest as cancer; and

use of equipment and exposure settings designed for adults may result in excessive radiation exposure if used on smaller patients.

The medical community has emphasized dose reduction in CT because of the relatively high doses of CT exams and their increased use, as reported in the National Council on Radiation Protection and Measurements (NCRP) Report No. 160. However, the increased radiosensitivity of pediatric patients compared to adults makes it important to adjust equipment settings to optimize radiation exposure to pediatric patients for all types of X-ray imaging exams.

If there is a medical need for a particular imaging procedure and other exams using no or less radiation are unsuitable, then the benefits exceed the risks, and radiation risk considerations should not influence the physician’s decision to perform the study or the patient's decision to have the procedure. However, "As Low as Reasonably Achievable" (ALARA) principles should always be followed when choosing equipment settings to minimize radiation exposure to the pediatric patient.

provide health professionals with guidelines enabling them to use the imaging equipment already in use at their facilities safely on pediatric patients.

As well as working with manufacturers and imaging experts to improve x-ray imaging devices, the agency is engaged in broad outreach efforts to incorporate radiation protection principles into facility quality assurance and personnel credentialing and training requirements.

The FDA seeks to lessen the burden necessary for medical professionals to safely use X-ray imaging devices on pediatric patients by:

encouraging manufacturers (through publication of FDA guidance) to consider radiation safety of pediatric populations in the design of new X-ray imaging devices; and

encouraging discussions among manufacturers and pediatric imaging experts on improvements to device design and instructions for use.

Facilities should look for special pediatric use features when purchasing new X-ray imaging equipment, but should be aware that their current equipment, which may lack special pediatric features or instructions, may still be in use for many years. FDA is not suggesting that facilities immediately replace their older equipment. Instead, imaging team members (e.g., physician, radiologic technologist, and medical physicist), should work together to appropriately configure older equipment for use on pediatric patients. Organizations such as the Alliance for Radiation Safety in Pediatric Imaging (ARSPI) provide free instructional materials on how to safely use X-ray imaging equipment on children. FDA has reviewed ARSPI’s instructional materials and believes they are appropriate. Hospital administrators should make radiation safety of pediatric patients a priority by actively encouraging their staff to make use of this information.

Examples of FDA medical radiation protection activities include:

"Initiative to Reduce Unnecessary Radiation Exposure from Medical Imaging," released February 2010. The focus of the initiative is the high-dose modalities (CT, fluoroscopy, and nuclear medicine); however, conventional X-ray exams, while comparatively low dose, are of special concern for the pediatric population because they are performed much more frequently.

Draft guidance for manufacturers entitled “Pediatric Information for X-ray Imaging Device Premarket Notifications” (which, once final, will only apply to new X-ray imaging devices, including CT, fluoroscopy, and general and dental radiography). The purpose of the guidance is to encourage manufacturers to consider radiation safety of pediatric populations in the design of X-ray imaging devices. A public meeting entitled "Device Improvements for Pediatric X-ray Imaging" (July 16, 2012) will be held to solicit comment on the draft guidance and broader radiation safety issues for use of X-ray imaging devices on pediatric populations.

Collaborations with the Alliance for Radiation Safety in Pediatric Imaging (ARSPI) and industry (through the Medical Imaging and Technology Alliance (MITA)) to develop educational tools and training materials to reduce dose to pediatric patients. The Image Gently/FDA Digital Radiography Safety Checklistis now available. Ongoing collaborative efforts include a survey of technique factors for pediatric digital radiography and an FDA-funded project to develop training materials for radiation safety in pediatric fluoroscopy.

Medical Community and Industry Activities

Efforts to protect pediatric patients from unnecessary radiation exposure during X-ray imaging procedures are not new. Some activities include:

The Alliance for Radiation Safety in Pediatric Imaging (ARSPI) has held two vendor summits for CT (2008) and Digital Radiography (2010).

ARSPI has launched the following radiation safety campaigns:

"Image Gently" for CT

"Step Lightly" for interventional radiology

"Pause and Pulse" for fluoroscopy

"Go with the Guidelines" for nuclear medicine

ARSPI has partnered with the American Academy of Oral and Maxillofacial Radiology to address concerns specific to pediatric dental radiography.

Much of the focus of professional groups and industry has been on reducing radiation exposure in CT because of the relatively high doses involved; for example, ARSPI and MITA collaborated on developing online CT modules for radiologic technologists; however, other types of X-ray imaging are still of concern. To address this, the FDA, ARSPI, and MITA are collaborating on projects aimed at reducing radiation exposure to pediatric patients during digital radiographyand fluoroscopy procedures. The resulting educational materials will be publicly available and add to the extensive information already available on the ARSPI website.

Information for Patients and Parents

The FDA recommends that medical imaging exams should be performed only after careful consideration of the patient's health needs. They should be performed only when the child's physician judges them to be necessary to answer a clinical question or to guide treatment of a disease. The clinical benefit of a medically appropriate X-ray imaging exam will outweigh the small radiation risk. However, efforts should be made to help minimize this risk.

The FDA recommends that parents:

Keep track of their child's medical-imaging histories as part of a discussion with the referring physician when a new exam is recommended (see the "My Child's Imaging Record" card, available from the Alliance for Radiation Safety in Pediatric Imaging).

Ask the referring physician about the benefits and risks of imaging procedures, such as:

How will the exam improve my child's health care?

Are there alternative exams that do not use ionizing radiation and are equally as useful?

Ask the imaging facility:

What safeguards are in place to mitigate the risks to my child? For example, does the facility use reduced radiation techniques for children?

Are there any additional steps that may be necessary to perform the imaging study (e.g., administration of a contrast agent, sedation, or advanced preparation)?

FDA has reviewed the following additional resources for parents and patients and believes they are appropriate:

Information for Health Care Providers

The individual risk from a necessary imaging exam is quite small when compared to the benefit of aiding accurate diagnosis or intervention. However, because of the increased risk of radiation exposure to younger patients, the FDA recommends that health care professionals and hospital administrators take special care in reducing radiation exposure to pediatric patients by following these steps:

Discuss the rationale for the examination with the patient and/or parent to ensure a clear understanding of benefits and risks.

determining if the examination is needed to answer a clinical question,

considering alternate exams that use less or no radiation exposure, such as ultrasound or MRI, if appropriate, and

checking the patient's medical imaging history to avoid duplicate exams.

Purchase equipment that is designed for use with pediatric patients, if possible, and request information from the manufacturer on how to properly configure the equipment for small patients.

Use the pediatric protocols or technique charts included with the equipment. If pediatric protocols or technique charts are not available for the currently marketed X-ray imaging device, ask the manufacturer or a pediatric imaging expert for assistance on how to appropriately use the device on small patients.

For existing equipment that may not have specific features or instructions for pediatric use, consult the general recommendations made by the Alliance for Radiation Safety in Pediatric Imaging. By consulting these recommendations, this existing equipment may be configured appropriately for use on children.

As part of a quality assurance program emphasizing radiation management, monitor doses to patients and check the facility doses against diagnostic reference levels, where available.

Justification: The imaging procedure should be judged to do more good than harm to the individual patient. Therefore, all examinations using ionizing radiation should be performed only when necessary to answer a medical question, treat a disease, or guide a procedure. The clinical indication and patient medical history should be carefully considered before referring a patient for any X-ray examination.

Optimization: X-ray examinations should use techniques that are adjusted to administer the lowest radiation dose that yields an image quality adequate for diagnosis or intervention (i.e., radiation doses should be "As Low as Reasonably Achievable" (ALARA)). The equipment used should be designed for pediatric use; the technique factors used should be chosen based on the clinical indication, patient size, and anatomical area scanned; and the equipment should be properly maintained and tested.

Communication between the referring physician and imaging team can help ensure that the pediatric patient receives an appropriate exam at an optimal radiation dose. Optimization of pediatric imaging exams should be carried out by a knowledgeable imaging team (e.g. imaging physician, technologist, and medical physicist). Note that there may be a range of optimized exposure settings for use on pediatric patients, depending on the capabilities of the imaging equipment and the image quality requirements of the physician. Radiation exposure may be optimized properly for the same exam and patient size at two facilities (or on two different models of imaging equipment) even though the radiation exposures are not identical.

The FDA's Center for Devices and Radiological Health defines the ages of the pediatric population as birth through 21 years. However, for purposes of obtaining a clinically acceptable image at an optimized radiation exposure, patient size, not age, is the controlling factor. This is because images are created by X-rays that pass through the body. These X-rays are absorbed as they pass through the body; larger patients absorb more X-rays than smaller patients, and therefore, generally require a higher radiation dose to generate images of the same quality.

It is important to note that there is considerable overlap between the sizes of larger pediatric and smaller adult patients. It is the patient’s size, not the patient’s age, that determines the dose needed for an optimal image for a particular indication. For example, based on a National Health Statistics report, a very small U.S. adult female is similar in size to an average 12-year-old child (male or female of similar size). If the same X-ray imaging exam is performed on adult and pediatric patients of the same size, the imaging parameters should be similar for both patients.

The risks of ionizing radiation-induced cancers depend on the amount of radiation received, the organ irradiated, and the age and gender of the patient. While the cancer risk per unit dose of ionizing radiation is higher for younger patients, the overall cancer risk is low for medical imaging exposures no matter what the age of the patient. If the X-ray procedure is medically necessary then the medical benefit will always exceed the cancer risk. Therefore, numerical cancer risk estimates should not be factored into the decision of whether or not a particular exam should be performed for a particular patient. The decision of whether an X-ray imaging exam is justified needs to be made by the child’s physician based on the medical needs of that particular child and the information the exam could provide. If there is a medical need for a particular X-ray procedure and other exams using no ionizing radiation (e.g., ultrasound and MRI) or less radiation are unsuitable, radiation risk considerations should not influence the physician's decision to perform the study or the patient's decision to have the procedure. However, ALARA principles should always be followed when choosing equipment settings.

Resources for Radiation Protection of Pediatric Patients

FDA has reviewed the following resources for referring physicians with a focus on justifying radiation exposure and believes they are appropriate:

FDA has reviewed the following resources for the imaging team (e.g., imaging physican, radiologic technologist, and medical physicist) with a focus on optimizing radiation exposure for pediatric patients and believes they are appropriate:

The joint FDA and Conference of Radiation Control Program Directors (CRCPD) Nationwide Evaluation of X-ray Trends (NEXT) program surveys radiation exposures for common procedures; these data have been used to develop diagnostic reference levels, which can be used by a facility to benchmark radiation doses for its imaging procedures in comparison to other facilities. Surveys of pediatric procedures were conducted in 1998 (pediatric chest) and 2005 (CT; data currently being analyzed).

Regulations and Guidelines Pertaining to Imaging Facilities and Personnel

Under the Mammography Quality Standards Act (MQSA), FDA regulates personnel qualifications, quality control and quality assurance programs, and accreditation and certification of mammography facilities. FDA also has regulations covering the safety and effectiveness and radiation control of all x-ray imaging devices (see the section "Information for Industry: X-ray Imaging Device Manufacturers and Assemblers"). Individual states and other federal agencies regulate the use of the x-ray imaging devices discussed on this webpage (CT, fluoroscopy, general and dental radiography) through recommendations and requirements for personnel qualifications, quality assurance and quality control programs, and facility accreditation.

Individual states have regulations and guidelines applying to imaging facilities and personnel. The Conference of Radiation Control Program Directors (CRCPD) publishes Suggested State Regulations for the Control of Radiation, which may be voluntarily adopted by states. A number of states are updating their regulations and guidelines to improve radiation safety.

FDA is working with the Environmental Protection Agency and the federal Interagency Steering Committee on Radiation Standards (ISCORS) to develop and publicize Federal Radiation Protection Guidance for Diagnostic and Interventional X-ray Procedures (FGR-14) on medical use of radiation in Federal facilities. While this comprehensive set of voluntary guidelines for pediatric and adult imaging was written for federal facilities, most of the recommendations are applicable to all X-ray imaging facilities and professionals. This draft document will be released soon.

Draft guidance for manufacturers on "Pediatric Information for X-ray Imaging Premarket Notifications" (covering CT, fluoroscopy, and general and dental radiography) has been published, with the goal of encouraging manufacturers to consider radiation safety of pediatric populations in the design of X-ray imaging devices. When finalized, this guidance will only apply to new devices. However, many currently marketed X-ray imaging devices have general indications for use that cover a broad range of clinical applications and populations; therefore, FDA encourages manufacturers to provide technical assistance to health care professionals on how to appropriately and safely use these older devices on pediatric patients.